ID.java Source code

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Here is the source code for ID.java

Source

/*
GNU LESSER GENERAL PUBLIC LICENSE
Copyright (C) 2006 The Lobo Project
    
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
    
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.
    
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
    
Contact info: lobochief@users.sourceforge.net
*/
/*
 * Created on Jun 7, 2005
 */

import java.util.*;
import java.util.logging.*;
import java.security.*;
import java.math.*;
import java.net.InetAddress;

/**
 * @author J. H. S.
 */
public class ID {
    private static final Random RANDOM1;
    private static final Random RANDOM2;
    private static final Random RANDOM3;
    private static final long globalProcessID;
    private static final Logger logger = Logger.getLogger(ID.class.getName());

    static {
        long time = System.currentTimeMillis();
        long nanoTime = System.nanoTime();
        long freeMemory = Runtime.getRuntime().freeMemory();
        long addressHashCode;
        try {
            InetAddress inetAddress;
            inetAddress = InetAddress.getLocalHost();
            addressHashCode = inetAddress.getHostName().hashCode() ^ inetAddress.getHostAddress().hashCode();
        } catch (Exception err) {
            logger.log(Level.WARNING, "Unable to get local host information.", err);
            addressHashCode = ID.class.hashCode();
        }
        globalProcessID = time ^ nanoTime ^ freeMemory ^ addressHashCode;
        RANDOM1 = new Random(time);
        RANDOM2 = new Random(nanoTime);
        RANDOM3 = new Random(addressHashCode ^ freeMemory);
    }

    private ID() {
    }

    public static long generateLong() {
        return Math.abs(RANDOM1.nextLong() ^ RANDOM2.nextLong() ^ RANDOM3.nextLong());
    }

    public static int generateInt() {
        return (int) generateLong();
    }

    public static byte[] getMD5Bytes(String content) {
        try {
            MessageDigest digest = MessageDigest.getInstance("MD5");
            return digest.digest(content.getBytes("UTF-8"));
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalStateException(e);
        } catch (java.io.UnsupportedEncodingException uee) {
            throw new IllegalStateException(uee);
        }
    }

    public static String getHexString(byte[] bytes) {
        // This method cannot change even if it's wrong.
        BigInteger bigInteger = BigInteger.ZERO;
        int shift = 0;
        for (int i = bytes.length; --i >= 0;) {
            BigInteger contrib = BigInteger.valueOf(bytes[i] & 0xFF);
            contrib = contrib.shiftLeft(shift);
            bigInteger = bigInteger.add(contrib);
            shift += 8;
        }
        return bigInteger.toString(16).toUpperCase();
    }

    /**
     * Gets a process ID that is nearly guaranteed to be globally unique.
     */
    public static long getGlobalProcessID() {
        return globalProcessID;
    }

    public static int random(int min, int max) {
        if (max <= min) {
            return min;
        }
        return Math.abs(RANDOM1.nextInt()) % (max - min) + min;
    }
}